Eglwys Mynydd Seion

Eglwys Mynydd Seion is an early Gothic style chapel built of rock-faced black basaltic stone, likely sourced from Penmaenmawr, with contrasting Bath oolitic limestone dressings and a slate roof. The main south front features a gabled central section with three closely spaced Gothic two-light windows, a roundel at the apex, and a lean-to narthex-porch gabled over the central moulded doorcase, which is angled at the head. Buttresses flanking the door rise as pinnacles, with triple windows on each side topped by a pierced balustrade. The central section is flanked by two-storey stair wings, each with similar two-light windows that have quatrefoil heads, and the upper windows are gabled.

On the east side, facing Chapel Street, there are three two-light windows beyond the stair wing, separated by buttresses, and gabled transepts at the north end featuring tall triple lancets with quatrefoil heads and a gable oculus. The north end culminates in a polygonal apse with a hipped roof, and almost detached from it is a vestry set at right angles under a separate roof.

The main body of the chapel consists of four bays, slightly tapering to the north before the transepts. It has plastered walls and a six-sided boarded vaulted ceiling supported by trusses that extend down to wall shafts and corbels. A west gallery is supported by octagonal cast iron columns. Behind the pulpit, there is an arch that contains an organ and console by P Conacher, enclosed in a Gothic case. The octagonal pulpit is positioned forward from its access gallery, which has flights of five steps at each end, all set within a semi-circular set fawr with a pitch-pine balustrade.

The pews, made of pitch pine, are arranged on a slightly raked floor in three banks, with additional pews in the transepts, accommodating a total of about 510 places plus the gallery. Doors on either side of the organ provide access to the vestry and a side entrance. The entrance narthex features patterned stained glass windows and triple arches that support the south wall of the chapel.